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The Opamp thread
Nov 1, 2019 at 8:05 PM Post #6,841 of 7,383
endia said:
buffers do not amplify signal voltage, it's output is same as the input voltage.. using it in the gain stage is pointless..
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This would explain why it’s awesome when you have circuitry that has one or two independent Buffer slots for specific buffer op amps to feed current to output stage (if I have this correct) and to “power” the audio op amps as the input and output remain the same!

Thanks for simple explanation. I’m afraid the internet doesn’t really do a great explanation in what the buffer does to the audio frequency in simple terms!

Side note: I have a portable player with adequate power supply and some legendary op amps I’ve rolled sound exactly how people on this thread and others say they sound like!

I’m curious about coupling film caps because this particular circuitry has them surrounded around the Dip8 and they sound better to my ears but it could be a placebo effect (I’d like to know what the advantage of coupling film caps around an op amp (if any??)

Btw: this player https://www.cssbuy.com/item-584795097581.html circuitry is almost exactly like the Zishan DSD 699 but it’s got the ak4497eq Chip and drive any low impedence headphones. The screws aren’t your typical Philips so I ordered the wowstick electric screwdriver set on AliExpress but it sounds really good when I change only one op amp with a genuine AD8620.

It’s worth the upgrade to the Zishan DSD 699 if you wanted the extra stages like the latter!
 
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Nov 2, 2019 at 1:38 AM Post #6,842 of 7,383
HeyManslowdown97 said:
Maybe stupid question but is it possible to replace BUF634 with a single op amp like Opa627??
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Makes no sense, because OPA627 can be successfully used in voltage-amplification-gain (gains <=5) or in low-pass-filter stage, I see not one single reason to use it in unity gain as an output buffer that can sustain a max. current of 45mA, while BUF634 can handle a max. output current of 250mA.

HeyManslowdown97 said:
Also can the BUF634 be used a headphone driving output amp if you put two onto a SOP-to-Dip adapter. If so what sound signature would “buffer” op amp have like the BUF634??!
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BUF634 or LME49600 are designed to operate as output buffers, so these operational amplifier chips will always work perfectly as output current boosters.
In case you want to replace an existing dual-opamp from one of your amplifier, might be more helpful to know what is that headamp and maybe some internal pictures or even the schematic. Usually, a SOP-DIP8 adapter should work fine, although BUF634 can be found in both SO8 and DIP8 packages.


A basic schematic for a headamp with BUF634 used as output buffer would be the below one, taken from TI's datasheet:

BUF_634.png
 
Nov 2, 2019 at 1:52 AM Post #6,843 of 7,383
Nov 2, 2019 at 3:09 AM Post #6,844 of 7,383
Just tried the MUSES02 and compared it with the OPA2107. I gave it a good listen on my Whammy Amp with HD 650's (Mimby DAC). The MUSES02 does not have the same instrument separation and soundstage as the OPA2107. Because of this, the MUSES02 does not have the same life-like holographic quality as the OPA2107. Very disappointed as the MUSES02 is twice the cost. OPA2107 is just too good.
 
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Nov 2, 2019 at 3:39 AM Post #6,845 of 7,383
Nov 2, 2019 at 5:54 AM Post #6,846 of 7,383
raoultrifan said:
Makes no sense, because OPA627 can be successfully used in voltage-amplification-gain (gains <=5) or in low-pass-filter stage, I see not one single reason to use it in unity gain as an output buffer that can sustain a max. current of 45mA, while BUF634 can handle a max. output current of 250mA.


BUF634 or LME49600 are designed to operate as output buffers, so these operational amplifier chips will always work perfectly as output current boosters.
In case you want to replace an existing dual-opamp from one of your amplifier, might be more helpful to know what is that headamp and maybe some internal pictures or even the schematic. Usually, a SOP-DIP8 adapter should work fine, although BUF634 can be found in both SO8 and DIP8 packages.


A basic schematic for a headamp with BUF634 used as output buffer would be the below one, taken from TI's datasheet:

​
Click to expand...

Yea I totally get it. The thing that threw me off was that a buffer is considered an “op amp” so I wasn’t clear about it’s functionality as being a one-trick-pony so-to-speak!

How I understand it now is that when you do have a specific buffer amp you have a ton of options to drive your favorite op amp audio signature. This is a pretty near functionality if I have it correctly!
 
Nov 2, 2019 at 6:22 AM Post #6,847 of 7,383
FritzS said:
Please take an eye to the new BUF634A
https://www.ti.com/product/BUF634A
https://www.ti.com/lit/ds/symlink/buf634a.pdf
https://e2e.ti.com/support/amplifie...placement-of-the-BUF634-with-the-new-BUF634A-
Click to expand...

I have it. It is VERY powerful but I believe it needs the right circuitry and op amp to handle it in order to get its full effect and tame it because in my experience it does create noise with high gain. But again, this could be just me not understanding how to make it work properly!

The datasheets and evaluation boards help so much in this area I’m learning to keep parts stable and effective!
 
Nov 12, 2019 at 12:29 PM Post #6,848 of 7,383
Nov 12, 2019 at 2:03 PM Post #6,849 of 7,383
HeyManslowdown97 said:
Remembered this post and found a Dip8 adapter that’s pin-to-pin compatible but it only works when replacing the BUF634 for Ha-5002 on a Dip8. Hope this helps...

https://www.cimarrontechnology.com/product/browndog-110101-ha5002-to-buf634-adapter
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just a warning for those who want to replace buf634 (or any other buffer) with ha5002 as output buffer; ha5002 has not short circuit protection so plugging or removing the plug from the circuit is potentially risky to damage ha5002s..
 
Nov 12, 2019 at 2:23 PM Post #6,850 of 7,383
endia said:
just a warning for those who want to replace buf634 (or any other buffer) with ha5002 as output buffer; ha5002 has not short circuit protection so plugging or removing the plug from the circuit is potentially risky to damage ha5002s..
Click to expand...

Yep, so critical of a warning especially when modding because mistakes can/do commonly happen when DIYing and experimenting.

The more you know the better!


I just install the new BUF634A and it sounds great and I don’t feel the need for the supposed transparency I read about in the HA-5002!
 
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Nov 20, 2019 at 8:09 PM Post #6,851 of 7,383
Jan 11, 2020 at 12:53 PM Post #6,852 of 7,383
Hey fellas, Im just now getting into Opamps. So far the Muse02 really appeals to my ears. I am surprised that the differences are so clearly audible.
 
Jan 11, 2020 at 3:59 PM Post #6,853 of 7,383
redrol said:
Hey fellas, Im just now getting into Opamps. So far the Muse02 really appeals to my ears. I am surprised that the differences are so clearly audible.
Click to expand...
Yes OpAmps can make the big difference.
If you have a change, try Sparkos Labs discrete ones.
 
Jan 12, 2020 at 7:14 PM Post #6,854 of 7,383
Burson V5 is another great one to try. Between Sparkos and Burson you are jumping straight into the pinnacle of what opamps can do. The cheaper chip opamps are still fun to roll though and teach you what to listen for in opamps. AD797 and LME49720 and LME49860 are some staples that you should try. Playing with those, including the Muses 02, will show you what Burson and Sparkos deliver.
 
Jan 13, 2020 at 2:36 AM Post #6,855 of 7,383
I gave up on rolling opamps. Have fun guys.

FYI, I was rolling in my Zishan's and Walnut's. I did so only on the daps, those are crap.

I prefer real daps now like the Ziku HD-X10 and even though I can roll on it, I don't...
 
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